Goals are to define mechanisms through which hormones regulate cell proliferation and function. Studies will be focused in two main areas. Firstly, the enzymes which catalyze phosphorylation of tyrosine residues, the cyclic nucleotide-dependent protein kinases, and the interactions between these two enzyme systems will be studied. Enzymes catalyzing phosphorylation of tyrosine residues are associated with stimulation of cell proliferation, whereas activation of cAMP-dependent protein kinase is associated with inhibition of cell proliferation and stimulation of specific differentiated function. We plan to characterize these enzymes and to investigate interactions which determine cell proliferation and function. The tryosine-specific kinases, epidermal growth-dependent protein kinase and p60src will be purified, analyzed, and compared with respect to several properties, including substrate recognition, response to inhibitors, and structure of active centers. A-kinase and G-kinase will be compared by examining the phosphorylation and cyclic nucleotide binding sites in R(I) and G-kinase. Interactions between tryosine-specific and cyclic nucleotide-dependent protein kinase systems will be investigated by determining the effect of cAMP in vivo on EGF- or p60src-dependent phosphorylation of tryosine residues in cell proteins. The role of tyrosine phosphorylation in EGF function will be studied in mutants with altered growth responses to EGF. Mutants with altered responses to cAMP will be used to explore the interaction of A-kinase with EGF. The second major area of study is the relationship between growth and expression of inducible differentiated function in cells maintained under optimal physiological conditions. Proliferating and functional adrenocortical zona glomerulosa cells will be prepared to study the development of zonation of the adrenal cortex. The role of antioxidants and O2 concentration in maintenance of glomeruylosa specific function and in zonation will be investigated. The effect of lipid peroxidation on cell proliferation, response to growth factors, culture life span, substrate utilization, steroidogenesis, and ACTH responsiveness will be determined. These investigations which seek to extend knowledge of fundamental mechanisms which control growth and function are relevant to cancer, organ regeneration, and hormone action. Disciplines: Endocrinology/Cell Biology/Biochemistry.